1. Field of the Invention
The present invention relates to a thin-film magnetic head having a thin-film magnetic head element and a plurality of electrodes for electrically connecting the element to an external device and a method of manufacturing the thin-film magnetic head, and to a thin-film magnetic head material used for manufacturing the thin-film magnetic head and a method of manufacturing the material.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought with an increase in surface recording density of a hard disk drive. A composite thin-film magnetic head has been widely used which is made of a layered structure including a recording head (which may be called recording element in the following description) having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called AMR head or simply MR head. A reproducing head using a GMR element is called GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
In general, an AMR film is made of a magnetic substance that exhibits the MR effect and has a single-layer structure. In contrast, many of GMR films have a multilayer structure consisting of a plurality of films. There are several types of mechanisms of producing the GMR effect. The layer structure of a GMR film depends on the mechanism. GMR films include a superlattice GMR film, a spin valve film and a granular film. The spin valve film is most efficient since the film has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and suitable for mass production.
Besides selection of a material as described above, the pattern width such as the MR height, in particular, is one of the factors that determine the performance of a reproducing head. The MR height is the length (height) between the end of an MR element closer to the air bearing surface (medium facing surface) and the other end. The MR height is basically controlled by an amount of lapping when the air bearing surface is processed.
Performance improvements in a recording head have been expected, too, with performance improvements in a reproducing head. It is required to increase the track density of a magnetic recording medium in order to increase the recording density among the performances of a recording head. In order to achieve this, a recording head of a narrow track structure has been desired to be manufactured by processing the magnetic pole into the submicron order through the use of semiconductor process techniques. The magnetic pole made of a magnetic material having high saturation flux density has been desired in order to achieve the narrow-track recording head.
Another factor determining the recording head performance is the throat height. The throat height is the length (height) of the portion (called pole portion in the present invention) between the air bearing surface and the edge of the insulating layer electrically isolating the thin-film coil. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
As thus described, it is important to fabricate a recording head and a reproducing head appropriately balanced so as to improve performances of a thin-film magnetic head.
The manufacturing process of a thin-film magnetic head includes a wafer process for forming thin-film patterns on a wafer as a substrate and a lapping process for adjusting the throat height and the MR height by lapping. The wafer process includes a number of mask steps, film forming steps by plating and sputtering, etching steps by sputtering, dry etching, wet etching and so on, and lapping steps by chemical mechanical polishing (CMP) and the like. The performance and characteristics of the thin-film magnetic head may be modified by changing the track width of the reproducing element and the track width of the recording element and so on. Therefore, thin-film magnetic heads that meet a variety of needs of customers may be manufactured by determining the track width of the reproducing element and that of the recording element and so on, using masks that satisfy required specifications.
The manufacturing process of a thin-film magnetic head includes a number of steps and it takes an extremely long period of time to manufacture one product. Therefore, in order to manufacture the magnetic head having the performance and characteristics that meet the needs of the customer, it is required to carefully work out a detailed production plan so that the performance and characteristics of the magnetic head may be changed by photomask selection.
However, the needs of the customers are not limited to those relating to the performance and characteristics of the thin-film magnetic head that are determined in the wafer process but embrace the needs relating to a slider for retaining the magnetic head element and flying over the surface of a hard disk platter. The needs of the customers for a slider may be, for example, whether to choose a side element type slider or a center element type slider. The side element type slider is a slider wherein a thin-film magnetic head element is formed near an end of the slider in the direction orthogonal to the direction of air flow. The center element type slider is a slider wherein a thin-film magnetic head element is formed in the center of the slider in the direction orthogonal to the direction of air flow. The side element type slider and the center element type slider are typical sliders. In these days sliders are tend to be largely categorized into the above two types for satisfying the demand for the flying characteristics over the surface of the hard disk platter.
Reference is now made to FIG. 35 to FIG. 38 for describing the side element type slider and the center element type slider.
FIG. 35 is a schematic front view of a surface of the side element type slider in which a thin-film magnetic head element is formed. FIG. 36 is a schematic bottom view of the air bearing surface of the side element type slider. In FIG. 36 the arrow indicated with numeral 120 shows the direction of air flow. ‘LE’ indicates the air inflow end. ‘TR’ indicates the air outflow end. In the side element type slider, as shown in FIG. 35 and FIG. 36, a thin-film magnetic head element 111 is formed near an end of the slider in the direction orthogonal to the direction of air flow, in the vicinity of an end face (end face of air outflow end TR in this example) 110 orthogonal to the direction of air flow. On the end face 110, four pad-shaped electrodes 112 are provided for electrically connecting the magnetic head element 111 to an external device. The four electrodes 112 are connected to the magnetic head element 111 through four conductors 113. A rail 115 is formed in the air bearing surface of the slider.
FIG. 37 is a schematic front view of a surface of the center element type slider in which a thin-film magnetic head element is formed. FIG. 38 is a schematic bottom view of the air bearing surface of the center element type slider. Numeral 120, ‘LE’ and ‘TR’ of FIG. 38 are similar to those of FIG. 36. In the center element type slider, as shown in FIG. 37 and FIG. 38, the thin-film magnetic head element 111 is formed in the middle of the slider in the direction orthogonal to the direction of air flow, in the vicinity of an end face (end face of air outflow end TR in this example) 110 orthogonal to the direction of air flow. On the end face 110, four pad-shaped electrodes 112 are provided for electrically connecting the magnetic head element 111 to an external device. The four electrodes 112 are connected to the magnetic head element 111 through the four conductors 113. The rail 115 is formed in the air bearing surface of the slider.
However, it is impossible to change between the side element type slider and the center element type slider by simply changing a photomask in an intermediate step in the manufacturing process of the thin-film magnetic head. It is therefore required in related-art techniques to prepare different sets of masks for the respective types of sliders and separately manufacture the sliders in volume.
In a hard disk drive for high density recording, a plurality of hard disk platters such as four or six platters are placed on top of one another. FIG. 39 illustrates an arrangement of thin-film magnetic heads in such a hard disk drive using a plurality of platters. A plurality of hard disk platters 122 are held by a rotating axis 121 in such a hard disk drive. The hard disk drive includes a thin-film magnetic head (called up-type magnetic head in the following description) 123, placed beneath the platter 122, whose medium facing surface faces upward; and a thin-film magnetic head (called down-type magnetic head in the following description) 124, placed above the platter 122, whose medium facing surface faces downward. The up-type magnetic head 123 and the down-type magnetic head 124 are coupled to a moving arm 125 through a suspension 126. The structural difference between the up-type magnetic head 123 and the down-type magnetic head 124 is the difference in position of the reproducing element and the recording element.
Accordingly, two kinds of the side element type slider and the center element type slider are each required for the up-type magnetic head and the down-type magnetic head. The total of four kinds of thin-film magnetic heads are thus required. In related-art techniques different sets of masks for twenty to thirty mask processing steps are prepared for each kind of magnetic head and magnetic heads of each kind are produced in volume. In a planned production, different mass-production lots are prepared for the respective kinds of magnetic heads for manufacturing magnetic heads that meet the customer's needs.
In the related-art techniques thus described, thin-film magnetic heads are produced, using different masks or different mass-production lots for the respective kinds of magnetic heads. As a result, a cycle time, that is, a period of time between an order and a shipment is long and manufacturing costs are raised.
In particular, modifications and improvements in specifications of hard disk drives are made in a short period of time in these days. The customers of thin-film magnetic heads therefore demand that the magnetic heads that meet desired specifications are supplied shortly after the order. Consequently, the manufacturer of thin-film magnetic heads is required to manufacture a variety of products in small quantities that meet specifications demanded by the customers in a short period of time. The above-mentioned problems are therefore noticeable.
Where the related-art techniques are used, there are many cases in which specifications required by the customer are modified in the course of mass-production of thin-film magnetic heads meeting the specifications and mass-production is required to be restarted from the first step. Consequently, waste results and manufacturing costs are raised.
Where the related-art techniques are used, the manufacturer of thin-film magnetic heads estimates the number of products to be ordered by the customer and specifications required and mass-produces magnetic heads prior to the order, in some cases, in order to strictly maintain the product shipping schedule of the customer or to beat the competitors by immediate delivery. However, the number of products ordered by the customer and specifications required may go far beyond the estimates of the manufacturer since the customer may quickly respond to the users' needs. In such a case the manufacturer has to keep a number of undelivered stocks and to produce new mass-production lots that meet the demand of the customer extremely quickly, regardless of the average cycle time. Since the specifications required by the customer or those of a final product change every six months, for example, in these days, undelivered products in stock for a couple of months are equivalent to nonconforming stocks to be wasted. Mass-production disregarding the average cycle time affects the balance of the mass-production line and reduces the mass-production capacities.
Techniques of forming two head elements in one slider and selecting one of the head elements for use are disclosed in Japanese Patent Application Laid-open Sho 61-296518 (1986), Japanese Patent Application Laid-open Hei 3-95715 (1991) and Japanese Patent Application Laid-open Hei 6-203330 (1994). The techniques allow most of photomasks to be common and to manufacture the up-type thin-film magnetic heads and the down-type thin-film magnetic heads.
In the techniques disclosed in the above-mentioned publications, however, the two heads elements are placed so that the magnetic poles of the two head elements face the same surface of the slider. Therefore, in order to form the up-type head element for the center element type and the down-type head element for the center element type in one slider through the techniques, there is no way but to place the two head elements side by side in a position near the middle of the slider in the direction orthogonal to the direction of air flow, in the vicinity of an end face orthogonal to the direction of air flow. Therefore, it is impossible to form the two head elements for the center element type both in the middle of the slider in the direction orthogonal to the direction of air flow, according to the techniques disclosed in the above-mentioned publications. Consequently, it is impossible in some cases to supply thin-film magnetic heads that meet the specifications required by the customer.
In Japanese Patent Application Laid-open Hei 8-87848 (1996), a technique is disclosed for forming rails on both sides of a slider and forming two head elements so that the tips of the head elements are placed on both of the rails. The technique allows the single slider to read and write data on neighboring two magnetic disk platters.
However, the technique requires pad-shaped electrodes for the two head elements. Eight electrodes are therefore required if the technique is applied to a composite thin-film magnetic head. It is difficult to place the eight electrodes in one slider. It is therefore difficult to implement the technique.